“It didn’t display any of the typical suspicious identifiers like misspelled words, badly typed or badly written addressing, excessive postage, a return address that doesn’t match up with the postmark as far as cities go,” the chief said. “It wasn’t marked ‘person’ or ‘to the attention of.’ ”

Addressed to the school, the envelope was well typed, he said.

The office worker who opened the envelope about 2 p.m. found a white powder and a typed message referring to Al-Qaeda, Bycholski said.

Being careful not to spill any of the powder, the staff person put the envelope in a plastic folder, double-taped it shut, left the office and closed the door and called 9-1-1-, the chief said.

A regional Haz-Mat team performed preliminary field tests and determined that the powder contained no explosive or radiological substances, Bycholski said. State and federal authorities will conduct further analysis for proteins or biological substances, he said.

According to the Hartford Courant, the two schools and the Waterbury government building were to be closed Friday.

In Houston this week, envelopes containing white powder were received at Crockett, Barbara Bush and Condit elementary schools. The incidents remain under investigation, the FBI said.

In the Dallas area, eight such incidents were reported on Tuesday and Wednesday, according to the Dallas Morning News.

In autumn 2010, the FBI investigated 17 reports of envelopes containing white powder at HISD campuses and more than a dozen such incidents at Dallas churches, mosques, businesses and schools. The envelopes contained a short message with a cryptic reference to al-Qaeda, officials said.